1. Technical Field
The present invention relates generally to computer systems networks, and more specifically to a system and method for reporting network connectivity information.
2. Background Art
Computer networks are becoming increasingly common. Large numbers of devices, including general purpose computer systems, input/output terminals, and special purpose peripherals, may often be linked into a single network.
Many different network protocols are currently in use. Examples of common, high level protocols include System Network Architecture (SNA), produced by IBM Corporation and ROLMLINK, produced by ROLM Systems Inc.. Other examples of network interconnection techniques are found in U.S. Pat. No. 4,466,063, SYSTEM INTERCOMMUNICATION PROCESSOR USED IN DISTRIBUTED DATA PROCESSING SYSTEM; and U.S. Pat. No. 4,412,285, MULTI-PROCESSOR INTERCOMMUNICATION SYSTEM AND METHOD.
A wide variety of physical device interconnection techniques are also in common use. Networked devices may be connected to a common communications bus, as is used in Ethernet networks. Another physical connection technique, used to connect two devices together using a twisted wire pair, is described in U.S. Pat. No. 4,642,805, DIGITAL LINK FOR TELEPHONE STATION SETS.
Several networks of the same type may be connected together using interface devices known as bridges. Other interface devices, sometimes referred to as gateways, may be used to connect together several networks of different types. Some networks become quite large, having several hundreds, or even several thousands, of devices connected together into a single network. In such systems, the interconnections between devices attached to the network may become quite complex, with switching systems providing multiple communication paths between a single pair of devices.
The devices attached to a large network may also display wide diversity. Such devices may include input/output terminals, other peripherals such as machine controllers and data gathering equipment, general purpose computers, network controllers, communication switching systems, telephones and various shared resources such as large capacity disk drives. Almost any type of computer system or component may be connected to a network.
In order to control function of the network, and keep track of resource usage, many network designs provide for one or more devices in a central network location to be designated as a network manager. A network manager may monitor traffic on the network, and may be able to control or influence message routing in some networks. The network manager often accepts error reports when malfunctions occur in devices attached to the network, and provides a centralized location where a person responsible for network operation may monitor the state of the network.
When a network error occurs, which is caused by failure of an attached device or component thereof, or a failure of a physical interconnection link, the location of the error may be very difficult to trace. A single failure may affect many different physical interconnections between devices, such as would happen when the power supply for a Computerized Branch Exchange (CBX) fails. Even a single-point physical failure may cause the failure of a large number of logical connections. This could happen for example, when a single optical fiber carrying a large number of communication channels is cut.
When failures occur in certain critical devices, a large number of error reports may be made to the network manager. Typically, every device which was supporting a communications link which passed through a failed device at the time of failure will report such communications failure to the network manager. These reports often reach the network manager at different times, and typically do not allow the network manager to pinpoint the source of the problem. If two independent failures occur at approximately the same time, the difficulties of determining the source of the errors is compounded.
Some networks attempt to minimize the amount of redundant error reporting which occurs to the network manager by providing intermediate devices which coordinate the error reports of several devices below them in the network hierarchy. Also, critical network resources may be designed to contain redundant subsystems in order to minimize the impact of a single subsystem failure. An example of such a redundant system may be found in U.S. Pat. No. 4,634,110 FAULT DETECTION AND REDUNDANCY MANAGEMENT SYSTEM.
One reason it is often very difficult to track down a single failure which gives rise to multiple error reports is that the network manager doesn't have knowledge of all the details of the physical interconnections between the devices of the network. Individual devices may be attached to and removed from the network quite easily, and may be moved from one connection point to another without a report being made to a central authority. This is especially true in environments such as Integrated Systems Digital Networks (ISDN), in which a terminal device may be moved from one connection to another simply by changing the location of a modular wall plug. Although the interconnection graph of a network is relatively static in that most devices are rarely moved, it is possible to change such graph quite drastically in a short period of time. Since network interconnections are so flexible, it is difficult to provide a current connectivity graph which may be used by the network manager to determine the location of a failure when multiple error reports are caused by a single failure.
It would be desirable to provide a method which would provide current network configuration information to a network manager. It would also be desirable for reports on network configuration changes to be made automatically. It would further be desirable for a network manager to be able to correlate multiple error reports in order to determine the location of a device failure.